There is a work machine such as a hydraulic excavator which adopts a pump flow rate controller controlling the pump flow rate in a positive fashion through the control of a regulator (pump flow rate control valve) in accordance with the operation of an operation device. A pump flow rate controller of this type includes, apart from one which directly controls a pump flow rate control valve with the operation pressure of a pilot operation type operation device, one which determines a target pump flow rate by a controller on the basis of the operation pressure to control the pump flow rate control valve (See Patent Document 1, or the like).